Required prerequisites of a solid and lasting roadway repair are a clean vertical wall cavity routed to solid roadway material with a compacted base for shrinkage free adhesion and compaction of the new aggregate.
Numerous inventions have been proposed for speeding and reducing the cost of roadway repair. Much of the machinery was designed with a specific objective of reducing the number of personnel required for roadway repair. Almost all of these machines, however, require the vehicle to be in motion during repair activity. This deprives the operator of a direct view of the roadway area to be repaired. Further, since attention is diverted by concurrent vehicle movement, the operator cannot devote all efforts to repair work and ignore the vehicle driving operations. It is thus impossible for the operator to make required repairs with a high degree of care and accuracy. It is further impossible to localize repair work to a selected area.
It is desirable to provide a completely cleaned repair area to eliminate subsequent area cleanup of materials which, with prior devices, have been swept or air blasted to the roadway side or shoulder. Air blasting and/or sweeping the routed roadway material creates heavy dusting and air pollution.
U.S. Pat. No. 3,217,620 to Mindrum et al granted Nov. 16, 1965, discloses a roadway maintenance apparatus that is intended to eliminate the need for several vehicles and a crew for roadway patching procedures. The vehicle includes a movable tool support head on an extended beam that can be controlled from an operator's station to project ahead of the vehicle to a defective roadway surface area.
Mindrum's tool head includes a boring or routing head, a repair material delivery head, a tamper or roller, and an airblast surface cleaner. Repair material is delivered to the movable tool head from a hopper on the vehicle frame via a telescoping delivery chute enclosing an auger. The tool head is selectively operable to pivot any one of the tools about a horizontal axis into an operative position.
Patching is accomplished with the Mindrum apparatus first by driving the vehicle into position behind the repair site. The operator then uses controls in the control cab to extend the tool head over the site, and to pivot the router down to an operative position. The router is then operated to cut through the roadway surface and prepare a cavity. An air blast is used to clean the cavity of loose material. The auger is used to deliver fresh repair material into the cavity. The tamper or roller is then pivoted into operative position to compact the repair material into the cavity and complete the repair. A brush on the vehicle frame may then be used to clean away excess repair material.
U.S. Pat. Nos. 3,625,120 and 4,215,949 show vehicles having hoppers for containing and heating asphalt. The '49 patent describes the use of a hot air blast for cleaning a prepared cavity in preparation for receiving patching material. A tamper is provided for tamping the material. The '49 patent also shows use of an auger for supplying material from the hopper to a loading position for loading the material in a bucket arrangement. The '20 patent shows a hopper having a screw feed for feeding material to a nozzle at the front of the vehicle. A rake is provided for raking the material into a prepared cavity. A roller is mounted at the back of the vehicle frame for finish rolling the patching material.
U.S. Pat. No. 3,564,985 refers principally to a heating system for heating highway repair material over a broad surface prior to the addition of either an additional layer or the addition of asphalt resin material.
U.S. Pat. No. 2,732,197 shows a tamper movably carried on a pivoted frame.
U.S. Pat. No. 1,714,659 is principally concerned with supplying material to a patching site. However, of some interest is the fact that it discusses the possibility of adding old asphalt to the machine as the roadway surface is being cut from the roadway so as to provide some economy in the patching cost.
U.S. Pat. No. 4,172,679 to Wirtgen discloses a renewing device for road surfaces in which a number of individual surface repair tools are rigidly mounted to the vehicle frame forward of the operator's control cab. The vehicle must be moved to bring the various tools into position over the repair site and then carefully moved again to move the tools within the repair area.
The Mindrum machine and other roadway repair apparatus of knowledge do not include a vacuum system for pickup of roadway materials routed from a relatively deep cavity. It is desirable to vacuum routed materials and deposit them into a hopper for return to an asphalt aggregate mix plant for reuse. It is also desirable to provide for dust-free operation during cutting and routing a repair cavity, a completely cleaned repair area, and an economic factor resulting from reuse of the routed roadway aggregate.
The Mindrum machine and other roadway repair apparatus of knowledge do not embody a water vacuum system which will remove water or melted ice from a pothole, broken roadway shoulder or frostboil. Nor do any provide a movable torch for completely drying a roadway cavity to permit proper and lasting repair during any season or inclement weather condition.
The Mindrum machine and other roadway repair apparatus of knowledge do not embody a tack coat spray applicator for securely bonding repair aggregate to the routed cavity walls. They do not include a ram for tamping the routed cavity base which is required to eliminate sinking of the repaired area during traffic use. Nor do they include mounting of all repair tools on a carriage for controlled forward and back, side to side, and up and down movement within full view of the operator and within confinement of the vehicle framework. This provides for precise, level and accurate thrust control of all operating tools. They do not embody thermostatic heat control for maintaining accurate temperature control of the repair aggregate in the supply hopper and conveyors. It has been found that temperature control is desirable for proper application of the repair aggregate and its compaction into and adhesion to the repair cavity. They do not embody an inverted two-direction material spreader with applied heat for accurate and level spreading of the repair aggregate. Applied heat will cause the repair aggregate oil to surface, causing a dense and less porous repair surface.
All functions mentioned above and absent in known roadway repair apparatus are desirable for quick, timely, effective and complete repair of potholes, broken roadway shoulders, and frostboils during all weather conditions. A need, therefore, remains for a roadway repair vehicle that will perform all of these functions economically.